I found a screw (more like an M6) and pulled the pilot out. Guess what: metal speck on the valve seat down below. Some contamination on the walls that made it sticky. You can see a fair amount of scoring and marring on the valve body... Not bad for a tractor about my age. The pilot will go back in there for another few decades... Did not take a photo of the seat, but it looks good. Will decide later if I want to lap-it a bit or not (any advice on this? I would do it like for a regular head valve with minimal amount of paste and rotation action)

Here is the pilot body:
[img]https://drive.google.com/a/csimple.org/file/d/0B57xpBUFyOUkcXlFeUJ4RVN0NC0tWHRIM1M3emV3NWlUTU5R/view?usp=sharing[/img]

It is now moving smoothly, just like everything else, with the simple action of a small magnet and after a simple clean-up/re-lube.

Here is the test with the magnet: much better now!
[img]https://drive.google.com/a/csimple.org/file/d/0B57xpBUFyOUkQmtZMVc5Z2Z4UHVpVHdWWkZiemgyb29nTTc4/view?usp=sharing[/img]

For completeness: all is well, the tractor is fixed! It was a metal speck preventing the pilot valve's proper sealing action and general contamination that was preventing proper movement of said pilot valve...

Had to ditch the gaskets that were sourced for the job: very poor fit. Made them with generic paper and tack-it red stuff...

Replaced two o-rings and the plastic backing coil on the piston while in there. The main o-ring on the cylinder needed a weird plastic band to stay on while reassembling: nothing special, but a tad expensive at 23$CAD...

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